JOHANNESBURG — Just when it seemed the scandal over the bogus sign language interpreter at Nelson Mandela’s memorial had run its course, a cousin and three friends say he was part of a mob that accosted two men found with a stolen television and burned them to death by setting fire to tires placed around their necks.

Thamsanqa Jantjie never went to trial for the 2003 killings when other suspects did because authorities determined he was not mentally fit to stand trial, the four told The Associated Press on Monday. They spoke on condition of anonymity because of the sensitivity of the fake signing fiasco, which has deeply embarrassed South Africa’s government and prompted a high-level investigation into how it happened.

Their account of the killings matched a description of the crime and the outcome for Jantjie that he himself described in an interview published by the Sunday Times newspaper of Johannesburg.

“It was a community thing, what you call mob justice, and I was also there,” Jantjie told the newspaper.

Jantjie was not at his house Monday. His cellphone rang through to a message saying Jantjie was not reachable.

Instead of standing trial in 2006, Jantjie was institutionalized for a period of longer than a year, the four said, then returned to live in his poor township neighborhood on the outskirts of Soweto. At some point after that, they said, he started getting jobs doing sign language interpretation at events for the governing African National Congress.

Jantjie said that he has schizophrenia, hallucinated and believed he saw angels while gesturing incoherently just 3 feet away from President Barack Obama and other world leaders at the memorial Tuesday. Signing experts said his arm and hand movements were mere gibberish.

In the interview Thursday, Jantjie said he had been violent in the past “a lot” but declined to provide more details and blamed his violence on his schizophrenia, for which he said he was institutionalized for 19 months in a period that included time during 2006.

An investigation is under way by South African officials to determine who hired Jantjie as the onstage interpreter at the Mandela memorial service and if and how he received security clearance.

The officials have not said how long their investigation will take place, and reaching them for updates was difficult Monday, a public holiday in South Africa.